Theoretical uncertainties in extracting cosmic-ray diffusion parameters: the boron-to-carbon ratio

PAMELA and, more recently, AMS-02, are ushering us into a new era of greatly reduced statistical uncertainties in experimental measurements of cosmic ray fluxes. In particular, new determinations of traditional diagnostic tools such as the boron to carbon ratio (B/C) are expected to significantly reduce errors on cosmic-ray diffusion parameters, with important implications for astroparticle physics, ranging from inferring primary source spectra to indirect dark matter searches. It is timely to stress, however, that the conclusions inferred crucially depend on the framework in which the data are interpreted as well as on some nuclear input parameters. We aim at assessing the theoretical uncertainties affecting the outcome, with models as simple as possible while still retaining the key dependences. We compare different semi-analytical, two-zone model descriptions of cosmic ray transport in the Galaxy: infinite slab(lD), cylindrical symmetry (2D) with homogeneous sources, cylindrical symmetry (2D) with inhomogeneous source distribution. We tested for the effect of a primary source contamination in the boron flux by parametrically altering its flux. We also tested for nuclear cross-section uncertainties. (paper)